Cattle breeders keep track of certain characteristics of their animals in order to select animals with the best combination of desired traits. But "best" has been a subjective and inconsistent measure. Now, thanks to ARS research, breeders may refine their decision-making by focusing on profitability. To assess their animals, breeders keep track of growth traits, such as weights at birth, weaning, yearling, and maturity. They also measure carcass traits such as lean yield, marbling, and fat content, which are indicators of value to consumers. In addition, they record traits like the age when a female reaches puberty and her subsequent pregnancy. Breed associations take the information, combine it with each animal's genetic tree, and run it through a computer program to develop an expected progeny difference, or EPD. That lets breeders compare individual animals for individual traits. They would know, for example, that bull A was more likely to produce offspring with the desired marbling than bull B. But until now, the process has not been complete: Producers were left with the difficult task of combining the EPDs in an efficient manner. A refined system devised by an ARS geneticist allows breeders to use the EPDs to predict genetic potential for profit. With this system, breeders will be able to know how to most profitably trade off such features as changes in fat thickness and marbling. The complicated calculations are not yet available in a simple computer program for individuals to use. Their developer says producers will most likely get the information through Cooperative Extension Service specialists or breed associations as the lab passes on the technology.

Fort Keogh Livestock and Range Research Laboratory, Miles City, MT
Michael D. MacNeil, (406) 232-8213, mike@larrl.ars.usda.gov

Dairy producers could benefit from an enzyme supplement—for their cows. Bromelain, a mix of enzymes extracted from the stems of pineapple plants, helps keep the white cell count in cows' milk down in the range that fetches a premium price, according to a recent ARS study. U.S. dairy producers get an extra 20 cents per 100 pounds for milk having a cell count under a specified level. That level ranges from about 200,000 to 300,000 cells per milliliter, depending on which state tests the milk. Producers can't sell milk with cell counts above the legal limit. In the United States, that's 750,000 cells/ml. Canada and Europe have lower limits—500,000 and 400,000, respectively. In the study of 10 cows with average white cell counts slightly over 300,000, putting 75 grams of bromelain pellets daily in each cow's feed reduced cell counts by 100,000 on average during each of two trials. What's more, cell counts never surpassed the legal U.S. or Canadian limits when the cows got bromelain, as they sometimes did when left untreated. With bromelain, producers could have more days with cell counts in the premium price range—under 300,000.

Immunology and Disease Resistance Laboratory, Beltsville, MD
Max J. Paape, (301) 504-8302, mpaape@lpsi.barc.usda.gov

Mixing tiny glass beads with catfish feed helps researchers do a better job of measuring how much feed the fish consume. Until now, it's been difficult to measure how much food an individual fish eats daily, because all fish are raised together in a pond and fed simultaneously. Generally, catfish producers record feed intake based on simple observation, but this method assumes that fish consume all the feed delivered and that they all ete the same amount. ARS researchers adapted the new, innovative technique from salmon feeding studies—using tiny glass beads in the feed—and customized it for channel catfish. The opaque glass beads, about 0.4 millimeters in diameter, are mixed in low concentrations of about 1 percent of the feed. After feeding, catfish are anesthetized and x-rayed. This allows the beads to be counted so that an accurate calculation of feed consumed by each fish can be made. In indoor tank studies, scientists found different catfish strains consume feed at different rates. Fish with superior feed intake and conversion of feed into filet meat can be identified, so this trait can be incorporated into breeding programs. The researchers have perfected the technique even more by automating the bead-counting process. This allows scientists to view 600 scanned x-ray images a day, versus 200 images over a few weeks when done by hand. Automation is nearly 100-percent accurate.

Catfish Genetics Research Unit, Stoneville, MS
Jeffrey T. Silverstein,(601) 686-3591, jsilvers@ag.gov

Healthier and more productive cows that produce more profits for farmers and more abundant, higher quality milk for consumers is the goal of an ARS research project to map dairy cattle genes. The project integrates research from two key ARS animal labs: one that keeps tabs on traits like milk, fat, protein, and others that affect cows' health, vigor and profitability; and another that studies genes related to growth, disease resistance, and milk productivity. By wedding findings of both labs, researchers will integrate newly identified molecular markers with existing data sources to more accurately evaluate dairy animals' traits and to speed up the rate of genetic improvement. As a result, genes influencing important traits like mastitis resistance, milk yield, and fat and protein concentrations will be easier to identify and use in breeding decisions. Using genetic markers in estimating the genetic value of dairy cattle can accelerate the rate of improvement for milk production and other economically important traits.

Animal Improvement Programs Laboratory/Gene Evaluation and Mapping Laboratory, Beltsville, MD
Curtis P. Van Tassell, (301) 504-9271, curtvt@aipl.arsusda.gov